The present invention relates in general to mobile radio cellular systems.
More particularly, the present invention relates to changes in such systems associated with the introduction of new services, in particular of the multimedia type.
New high data rate services are presently being introduced into so-called xe2x80x9csecond generationxe2x80x9d mobile radio cellular systems such as, in particular, the GSM system (for xe2x80x9cglobal system for mobile communicationsxe2x80x9d), in addition to the voice services and the low and medium data rate services already provided by such systems. Examples of such high data rate services comprise circuit mode data services such as high speed circuit switched data (HSCSD), or packet mode data services such as the general packet radio service (GPRS).
In parallel, changes are taking place towards so-called xe2x80x9cthird generationxe2x80x9d systems, in particular the universal mobile telecommunication system (UMTS) that will make even higher data rates possible.
In general, and as shown in FIG. 1, a mobile radio cellular system can be represented as comprising a mobile radio cellular network itself comprising a radio access subsystem 1, serving essentially to manage radio and interface resources with mobile stations 2, and a network subsystem 3 serving essentially to manage calls and the interface with external networks 4, such as, in particular, the public switched telephone network (PSTN), the integrated services digital network (ISDN), etc.
In general, in a mobile radio cellular system, radio resources are allocated dynamically to mobile stations as a function of their requirements. More precisely, the radio resources allocated to a mobile station for a given service are selected by the radio access subsystem from a set of resources allocated to a given cell. The given cell is selected or reselected by the radio access subsystem in co-operation with the mobile station, with the mobile station having greater or lesser autonomy depending on circumstances, i.e. having a greater or smaller degree of control over the system in such co-operation. The various selection criteria used comprise, in particular, the radio resource requirements of the mobile station for the service under consideration, the availability of resources in various cells supporting the service, and the results of radio measurements for the various cells, for said service.
The resources allocated to a cell are also determined in application of known principles for sharing resources between cells within a cellular network, and they are also shared in fixed or dynamic manner between the various services supported by the cell.
Furthermore, in a mobile radio cellular system, radio resources are formed by xe2x80x9cmultiple-accessxe2x80x9d transmission channels, in particular using a combination of multiplexing techniques including frequency multiplexing. For example, in a system such as the GSM system, such combined multiplexing includes frequency multiplexing and time division multiplexing, with a transmission channel in this case being defined as a given time slot in a time division multiplex carried by a given carrier frequency.
A problem which arises with a mobile station that is accessing a plurality of services simultaneously, lies in the selected cell (and thus the frequency allocated in this way to the mobile station) possibly being different for the different services, in which case such a mobile station needs to be fitted with radio transceiver means suitable for switching very fast from one frequency to another, and possibly even for transmitting or receiving simultaneously on different frequencies. Such mobile stations suffer from the major drawback of being relatively complex and therefore expensive.
A particular object of the present invention is to avoid that drawback.
The present invention thus provides a system for allocation radio resources to a mobile station in a multiservice mobile radio cellular system in which radio resource allocation for the various services is performed independently, and in which the radio resources are formed by transmission channels having multiple access using combinations of multiplexing techniques including frequency multiplexing, the system essentially including coordination means for coordinating the allocation of radio resources for the various services accessed simultaneously by a mobile station, in order to allocate different channels carried by a single carrier frequency to the various services for said mobile station.
The present invention also provides a mobile station and an entity (such as a radio access sub-system) for a mobile radio cellular system that is usable in such a system.